Spinal cord stimulation for low back pain

116

An interview with James North

James North presented interim data from the MAP study—ongoing study evaluating the prevalence of multiple areas of pain in patients who are eligible for spinal cord stimulation—at the annual meeting of the International Spine Intervention Society (ISIS; 16–20 July, New York, USA). He spoke to Spinal News International about the use of spinal cord stimulation to manage low back pain.


What is the history of spinal cord stimulation for the management of low back pain?

Prior to 2004, spinal cord stimulation was only used to manage pain in the extremities because we had little success with using the technologies available at the time to treat low back pain. However, in 2004, Boston Scientific introduced a new approach to spinal cord stimulation. Their system was based on the technology used to restore hearing with cochlear implants, which involves precise controlled delivery of electrical impulses to various parts of the cochlea. Other spinal cord systems used similar technology to pacemakers, which is just delivering a certain amount of electrical impulses to the heart (ie. the delivery is less precise than with cochlear implants). With the new system, we are able to stimulate a patient’s lower back with relative consistency.


Which patients with low back pain are good candidates for spinal cord stimulation?


Spinal cord stimulation can be used to treat neuropathic pain but not mechanical pain. Therefore, you have to differentiate between patients with neuropathic low back pain and those with mechanical low back pain. Patients with neuropathic pain are typically those who will be in pain whatever position they are in whereas patients with mechanical pain often have much less pain when they are lying down or do not have any pressure on their back.


Even if patient is a good candidate for spinal cord stimulation, they have to undergo a trial period (typically, seven to 10 days) of spinal cord stimulation before receiving a permanent implant. The trial uses needles; there is no operation involved. If they have a successful trial, meaning that they have a greater than 50% improvement in their pain, they receive a permanent implant and an incision is made under the skin to insert the battery.  


How many patients have a successful trial and what are the reasons for a failed trial?


In my own practice, of those with back pain issues, about 85% will go on to receive a permanent implant. However, some patients will find the sensation of the therapy irritating or just not soothing. I find that the most consistent population who cannot tolerate the paraesthesia—or “tingling”—of the therapy are those, particularly elderly patients, who have a lot of numbness associated with their pain. 


What are the key objectives of the MAP study?


The MAP study will provide a snapshot of patients that have multiple areas of pain. At the moment, the tools we have for assessing pain—for example, the Visual Analogue Scale (VAS) or the Numerical Rating Scale (NRS)—do not gauge pain in distinct areas as they are more of a global assessment of how much a patient is in (rather than where they are in pain). This makes assessing distinct areas of pain difficult, so the MAP study is attempting to break down pain into different areas and provide a score for each of those areas. Actually, it has broken down pain into 47 different areas across the body. It should provide us with a very useful tool for assessing patients with multiple areas of pain, which really accounts for the majority of patients with chronic pain.


Another study, OPTIONS [the interim results of which were also presented at ISIS] is evaluating the efficacy of Boston Scientific’s new 32-contact spinal cord stimulation device (Precision Spectra) in patients with multiple areas of pain.


What further studies of spinal cord stimulation therapy are needed?


Large multiple-centre controlled studies would be valuable, as would head-to-head trials of the different available spinal cord stimulation technologies. It is worth noting that during spinal cord stimulation trials, in addition to their own leads, the Boston Scientific device is unique in that it can be connected to St. Jude Medical or Medtronic leads. It would be interesting to compare the effectiveness of Boston Scientific’s device using all three systems’ leads; their own vs. Medtronic’s or St Jude Medical’s.


James North is a pain specialist with the Carolinas Pain Institute and assistant professor at Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina, USA. He is a paid consultant of Boston Scientific Neuromodulation Corporation